New Radiator Install - proper block flush

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Joined
Apr 22, 2024
Messages
23
Reaction score
21
Location
Moorpark, CA
My Car
71 Mach , 351C, 4 Spd Top Loader
It was a great Memorial day drive with the Mach 1 this weekend, beautiful So. Cal weather in Ventura. Then the radiator decided to blow a hole in itself.
I'm going to replace it with a Champion CC381 3 core, add an expansion tank and of course change the hoses and Tstat.
Here is my question:
I want to flush the cooling passages before installing the new radiator. I'm anticipating that I will find all kinds of junk coming out. I'm not wanting to pull the engine.
  1. Should I pull the freeze plugs?
  2. Should I just take out the pipe plugs?
  3. Is there a chemical that I should use?
  4. What is the max pressure to use when flushing?
  5. Anything special that I should do with the WP?
If I have missed anything, please help me out.
Thanks for your help
Charlie B
 
Other than old coolant, why would there be gunk in the water passages ?

I would put in the new radiator. Remove the thermostat. Fill system with fresh coolant. Run the car for an hour. Drain the coolant, and refill it with more fresh coolant. Put the thermostat back in.
 
If the car ran fine and didn't overheat before, I would just do a hose flush until everything runs clear. You can hook up to the block coolant pipe and flush the system out the water pump inlet. Leave the thermostat in place, as that will help force the water into the engine.

Be sure you have a Cleveland specific thermostat with the "hat".
 
Other than old coolant, why would there be gunk in the water passages ?

I would put in the new radiator. Remove the thermostat. Fill system with fresh coolant. Run the car for an hour. Drain the coolant, and refill it with more fresh coolant. Put the thermostat back in.
Rust and corrosion from somebody filling up the radiator with a garden hose.

And little chunks of RTV where somebody got overzealous with it installing the water pump or thermostat housing.

Little chunks of metal from when the spring in the lower radiator hose rusted and broke apart.

Some sort of snake oil in a bottle somebody had purchased from the auto parts store and dumped in. Radiator stop leak or something that promised to give you 5HP.

Hell, I was watching an episode of powernation where they tore into a junk yard motor and there was a rusted bolt sitting there in the water passage. No clue what a previous owner did to the thing for that to happen.
 
Rust and corrosion from somebody filling up the radiator with a garden hose.

And little chunks of RTV where somebody got overzealous with it installing the water pump or thermostat housing.

Little chunks of metal from when the spring in the lower radiator hose rusted and broke apart.

Some sort of snake oil in a bottle somebody had purchased from the auto parts store and dumped in. Radiator stop leak or something that promised to give you 5HP.

Hell, I was watching an episode of powernation where they tore into a junk yard motor and there was a rusted bolt sitting there in the water passage. No clue what a previous owner did to the thing for that to happen.
Good points. If this particular car was cared for and serviced , maybe not too bad.
 
Google Mercedes citrus flush. I did this after doing a hose flush where it was running clear coming out. I was shocked at what came out with this.
 
Rinsing a block out with hose water shouldn't hurt it. These things were designed back when doctors were smoking cigarettes while delivering your baby and kids grew up drinking from the garden hose.

If a little hose water hurts your engine, it was too much of a princess anyways. :D
 
If the car ran fine and didn't overheat before, I would just do a hose flush until everything runs clear. You can hook up to the block coolant pipe and flush the system out the water pump inlet. Leave the thermostat in place, as that will help force the water into the engine.

Be sure you have a Cleveland specific thermostat with the "hat".
I like this concept. I’m going to give it a try.
All the replies are good. I didn’t know that there is a specific stat for Cleveland’s, that a a good tip.
I will google the Mercedes citrus flush.
I will start this project next week and reply to the post to update everyone.
Comments are still welcome, I need all the wisdom I can get.
Thank you
 
Rinsing a block out with hose water shouldn't hurt it. These things were designed back when doctors were smoking cigarettes while delivering your baby and kids grew up drinking from the garden hose.

If a little hose water hurts your engine, it was too much of a princess anyways. :D
OK 'Pune, next thing you're going to tell us is "Kids can drink water out of the garden hose and play Jarts without exploding" ;)
 
Good points. If this particular car was cared for and serviced , maybe not too bad.
You never know what might be in your block. My brother purchased a 71 Mach I M code new. A couple years later, I bought it from him. Long story short, while returning home from work in 1980, it overheated. After it cooled off, I removed the thermostat, suspecting its failure the cause of the overheating. Quite surprising, it could NOT OPEN because a very rusty 1" diameter ball bearing was blocking the opening of the thermostat. Apparently, some assembly line ford employee had gotten bored and dropped that ball bearing in before assembling the thermostat. It had been working around in the motor for 9 years and 130,000 miles before it caused a problem. In the meantime, I had flushed the engine at least two timed with rust mostly being an issue. I had also changed thermostats at least twice and the ball bearing was not visible when I changed thermostats.
 
If the car ran fine and didn't overheat before, I would just do a hose flush until everything runs clear. You can hook up to the block coolant pipe and flush the system out the water pump inlet. Leave the thermostat in place, as that will help force the water into the engine.

Be sure you have a Cleveland specific thermostat with the "hat".
HeniKiller has offered some sound direction. I have only one further suggestion. I have seen a lot of cooling systems with scaling and corrosion causing problems with cooling systems. I stopped using antifreeze/coolant concentrate, where the concentrate is mixed 50/50 with water. Rather, I use premixed coolant. Why? Because in most places the tap water is hard water, with a lot of dissolved mineral content, Despite the coolant concentrate having chemicals in it that help minimize the adverse impact of those dissolved solids, often those dissolved solids end up plugging cooling tubes and creating scaling on the surfaces of the cooling system.

As for a coolant brand, I personally use Prestore Premixed coolant. There are other manufacturers with fine products also. But, this is what our local parts stores carry in pre-mixed form.
 
I bought this tool to help me flush the block.


I'll use for the heater core and use it to power flush the block using Hemikiller's suggestion.
Regarding premixed Vs. concentrate; I think that premixed uses distilled water vs tap water. From all of the info I've been gathering, distilled water is overwhelmingly suggested when using a concentrate.
 
Whatever you do, do not use distilled water by itself: it is fairly acidic and needs the ethylene glycol to neutralize the acidity. You can buy distilled water in most grocery stores, as it is what is recommended for irons. Ask your wife if she remembers ironing...*G*
 
It was a great Memorial day drive with the Mach 1 this weekend, beautiful So. Cal weather in Ventura. Then the radiator decided to blow a hole in itself.
I'm going to replace it with a Champion CC381 3 core, add an expansion tank and of course change the hoses and Tstat.
Here is my question:
I want to flush the cooling passages before installing the new radiator. I'm anticipating that I will find all kinds of junk coming out. I'm not wanting to pull the engine.
  1. Should I pull the freeze plugs?
  2. Should I just take out the pipe plugs?
  3. Is there a chemical that I should use?
  4. What is the max pressure to use when flushing?
  5. Anything special that I should do with the WP?
If I have missed anything, please help me out.
Thanks for your help
Charlie B
I used Prestone super flush for many years and always had good results. Change the T stat, radiator and heater hoses as well. I used filtered water from my tap. Nuff said.
 
HeniKiller has offered some sound direction. I have only one further suggestion. I have seen a lot of cooling systems with scaling and corrosion causing problems with cooling systems. I stopped using antifreeze/coolant concentrate, where the concentrate is mixed 50/50 with water. Rather, I use premixed coolant. Why? Because in most places the tap water is hard water, with a lot of dissolved mineral content, Despite the coolant concentrate having chemicals in it that help minimize the adverse impact of those dissolved solids, often those dissolved solids end up plugging cooling tubes and creating scaling on the surfaces of the cooling system.

As for a coolant brand, I personally use Prestore Premixed coolant. There are other manufacturers with fine products also. But, this is what our local parts stores carry in pre-mixed form.
This is why the pre-mixed costs more than the concentrate. https://goglycolpros.com/blogs/ask-...pany recommends,used in heat transfer systems. Chuck
 
A cooling system flush is one of the more basic maintenance services, along with oil changes, rotating tires, and battery maintenance , that every gas station and general mechanics garage performed daily. No rocket science here. Generally, there is a flushing solution, or cooling system cleaner that you can buy at most any auto parts store. Just pour it in your radiator, and run the car for the directed amount of time, then, pull your lower hose at one end to drain it all out. Since most people will want to replace the t-stat anyway, remove it and bolt the t-stat housing back on for now. You can "back-flush from the upper hose, or flush in the normal direction from the bottom, whichever is easier for you. Flush with water, yes, the garden hose, until all clear. Install the new thermostat, connect hoses back up, fill with plain water again, for pressure test, ( you can't compress a liquid, is why the water fill again). If all is sealed, drain the water out, you can use the petcock this time, and refill with proper water/coolant mix. It's very simple, just don't drain the system on your nice concrete driveway unless orange rust stains and anti-freeze remnants that won't evaporate appeal to you.
 
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